This invention relates to a method and apparatus for regenerating used active carbon.
Active carbon has been used extensively in many engineering fields, and recent trends of preventing or minimizing public hazard, especially contamination of river and sea water require to use a large quantity of active carbon. Accordingly, it is necessary to regenerate or reactivate used active carbon.
Since active carbon that has been used to purify contaminated water, such as factory waste water, is wet when it is taken cut from the purifying apparatus, in order to regenerate it it is necessary to first heat it to remove moisture and then increase its heating temperature for decomposing and carbonizing contaminants deposited on the particles of the active carbon. Then the temperature is maintained at a temperature between 500.degree. C. to 1,000.degree. C. for a certain interval which varies depending upon the type of the contaminants deposited or adsorbed, thereby reactivating the carbon. For the purpose of decomposing carbonaceous deposit, it is necessary to introduce steam and CO.sub.2 gas into the heating chamber containing used activated carbon to be regenerated. Then, the resulting carbonaceous material can be removed by the following reactions EQU C+H.sub.2 O=CO+H.sub.2 EQU C+CO.sub.2 =2CO
Among a number of types of prior methods of regenerating used active carbon are included (1) an externally heating system in which a vertical cylinder containing fluidized used active carbon is heated from outside by hot gas, flue gas for example, and steam and CO.sub.2 gas are introduced into the bottom of the cylinder, (2) an electric arc type in which used active carbon is admitted into one end of a rotary cylinder and heated by electric arcs struck between a plurality of electrodes which are mounted on the inner surface of the cylinder in the radial direction thereof. If the active carbon is wet it is necessary to introduce steam into the cylinder, and (3) Herrishoff type in which a plurality of vertically spaced shelves and a plurality of rotary distributors are mounted in a vertical cylinder. The used active carbon is introduced into the upper portion, and steam and a mixture of liquid fuel and air are supplied into the lower portion of the cylinder. While being successively transferred onto lower shelves, the used active carbon is heated by the combustion product of the fuel and reacts with the steam and CO.sub.2 gas contained in the combustion product. These prior art methods and apparatus are not advantageous in that they require a source of steam and a source of heating gas, the loss of pulverized active carbon is large, and the cost of installation and operation is large.